Patent GB-492339-A (GB)
Title: A new or improved method of and apparatus for manufacturing metal cinema projection screens
IPC: G03B21/56
Filed: 1937-03-16
Abstract: 492,339. Making kinema projection screens ; milling. STABLEFORD, J. L. March 16, 1937, No. 7740. [Classes 83 (ii) and 83 (iii)] In a method of and apparatus for making a kinema screen particularly a screen of the kind described in Specification 468,705, a metal sheet is supported so that it coacts with one or more milling cutters or sets of cutters which are moved relatively to the strip to form a series of staggered slots in the sheet. The strip 5 for the screen is passed from a drum 4 through tensioning jaws 6, 7 arranged at each end of the frame 1. The lower left-hand jaw 7, Fig. 2, is secured through members 9 to cross members 10, 11 connected together with intermediate rubber members 12. The jaws may be pressed together against the action of springs 14 by means of screws. The right-hand jaws are of similar construction and are connected through rods 17 to a bar 18 which may be operated by a hydraulic jack 19 to tension the strip. The cross member 23 may be adjustable to vary the length of strip under operation. The cutter-spindles 27, 28 each carry a gang of rotary slotting-cutters 25, 26 and are belt driven from a motor 31 mounted on the travelling cutter carriage 35 which has rollers 36 running on the frame 1. To traverse the carriage a manually operated handle 37 drives a shaft 38 chain geared to a shaft 43 carrying wheels 44 engaging fixed racks or chains 45. The shaft 43 carries a lever arm 46 moving over an arcuate member 47. The strip passes between guide cheeks 48, 49 the former secured to a bar 50 secured to a member 51 pivoted on the carriage and the latter secured to a bar 52 pivoted to member 51. The cheeks 48, 49 may be secured together for simultaneous pivotal movement to lift the strip away from the cutters for movement from one slotting position to the next. The frame 32 carries a lubricant tank 62 connected to transverse tubes 63 to convey lubricant to the cutters. Large diameter cutters 67 are provided one at each of opposite ends of the spindles 27, 28 to trim the edges of the strip. A brush 70 driven from the motor 31 acts in conjunction with a scraper 71 to remove burrs and chips from the work. In operation after the strip has been positioned and tensioned the cheeks 48, 49 are closed onto the strip and a slot is cut by each of the cutters 25, 26. When each cutting stage is completed the strip is lifted from the cutters by means of a handle actuating a cam 55 to lift the bars 50, 52 together. The handle 37 is then operated to move the carriage longitudinally until arm 46 engages an abutment 58 carried by member 47. The cutters are then positioned for another slotting operation, these operations being repeated until the carriage reaches its left-hand position after which it is returned and a fresh section of the strip is drawn off the drum 4. The spacing may be varied by altering the amount of the intermittent carriage movement. In a modification the cutters may be intermittently moved instead of the strip. Or a single cutter may be employed which may be re-set longitudinally to stagger the rows of slots. In another modification the strip may be fed relatively to the carriage and reclamped for each adjustment.